Wearable exoskeletons have been designed for medical, commercial and military applications. Medical exoskeletons are designed to help restore a user's mobility. Commercial and military exoskeletons help prevent injury and augment a user's stamina and strength by alleviating loads supported by workers or soldiers during strenuous activities. Exoskeletons designed for use by able-bodied users often act to improve the user's stamina by transferring the weight of a tool or load through the exoskeleton structure and to the ground, thus decreasing the weight borne by the user. For the exoskeleton to transfer this weight to the ground, each exoskeleton support member and exoskeleton joint between the exoskeleton weight and the ground must be able to act as a conduit of this force around the user. This requires a degree of rigidity, seen in the joints of current exoskeletons, that can limit the range of motion of some exoskeleton joints. By limiting the flexibility at these joints, the mobility and maneuverability of the exoskeleton is reduced, thereby limiting the usefulness of the exoskeleton in certain applications.
Supporting the structure of an exoskeleton through a hip joint while maintaining a high degree of hip joint flexibility is one of the more difficult exoskeleton design challenges. In order to transfer weight effectively at the hip joint, many current exoskeleton designs utilize a hip joint with limited flexibility, particularly with respect to hip abduction and adduction. The flexibility of the hip of some exoskeleton designs is improved by adding an array of joints and movable members that extend away from the hip joint of the exoskeleton user. Such designs, in which the exoskeleton structure extends substantially away from the body of the exoskeleton user, result in a high level of relative movement between the exoskeleton legs and hips and the legs and hips of the user during some leg and hip movements. Differences in relative movement are undesirable for a number of reasons: they make exoskeleton movements less like the human movements that are intuitive to the exoskeleton user; and, importantly, they can result in translational movements at the legs that cause chafing between the user and the exoskeleton. Preventing this translational movement requires additional exoskeleton design features to allow the exoskeleton legs to extend or compress in order to maintain the same length as the user's legs. In addition, the added bulk of hip joints that extend away from the user can decrease exoskeleton maneuverability in tight spaces, increase exoskeleton weight and interfere with the motion of the exoskeleton user's arms.
Due to the limitations imposed on exoskeleton use by the restricted range of motion in exoskeleton hip joints, there exists a need in the art to develop a device that allows improved flexibility in weight-bearing exoskeleton hip joints. There exists a further need to develop joints in which the relative movement between the exoskeleton and the exoskeleton user is minimized and to develop joints that do not substantially increasing the bulk of the exoskeleton at the hip joints.